Cadherins are homophilic cell adhesion molecules that establish and maintain cell-cell contacts. Cadherins play important roles in tissue segregation during development and may have tumor suppressor activity. Cytoplasmic factors that regulate cadherins will be studied utilizing a dominant negative N-cadherin molecule lacking the extracellular domain. Injection into Xenopus embryos this molecule results in loss of cell-cell adhesion due to inhibition of endogenous cadherins. The specific aims of this proposal are: determine the cytoplasmic sequences responsible for the dominant negative phenotype, characterize cytoplasmic factors that interact with cadherins at these sequences, and analyze other cadherins for similar regulatory interactions. To identify the cytoplasmic sequences involved in N-cadherin regulation a dominant negative N-cadherin molecule containing cytoplasmic deletions will be injected into Xenopus embryos and analyzed for loss of cell adhesion. The role of the cytoplasmic sequences will be determined by transferring the sequences to new locations in N-cadherin and onto a heterologous transmembrane protein. Finally the cytoplasmic proteins that associate with the N-cadherin cytoplasmic domain will be isolated utilizing the yeast two-hybrid system for identifying proteins that can interact.